Scientists use radio waves to detect explosives

Scientists in Japan have developed a technique for detecting explosives using radio waves.

The scientists said the technique is better than conventional methods of detection such as X-rays, and can identify different types of white powder, from flour and salt to drugs and explosives.

The technique can also identify landmines, an improvement from traditional metal detectors that cannot tell bits of metal in the ground from an actual mine.

"Until now it has been very difficult to detect specific explosives such as TNT because they contain atoms of nitrogen that vibrate at very low frequencies," said Professor Hideo Itozaki at Osaka University.

"The natural frequency at which the nucleus of an atom vibrates is called its resonant frequency and the lower this is, the harder it is to detect what atoms are present in a molecule, which in turn makes it harder to define what the molecule or substance is."

The scientists created a device called superconducting quantum interference device (SQUID), which has a very sensitive magnetic-field sensor that detects nitrogen, an element found in many explosives, including TNT.

The SQUID operates at a temperature of -196°C.

"This will not hinder the equipment from being used in places such as airports, as liquid nitrogen is becoming much easier to deal with and is already routinely used in hospitals and laboratories," said Itozaki.

One disadvantage is that the screening time takes "several minutes', something the team is working to improve.